4.14-stable review patch. If anyone has any objections, please let me know.
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From: Mikulas Patocka mpatocka@redhat.com
commit 6e2fb22103b99c26ae30a46512abe75526d8e4c9 upstream.
Early alpha processors cannot write a single byte or word; they read 8 bytes, modify the value in registers and write back 8 bytes.
The type blk_status_t is defined as one byte, it is often written asynchronously by I/O completion routines, this asynchronous modification can corrupt content of nearby bytes if these nearby bytes can be written simultaneously by another CPU.
- one example of such corruption is the structure dm_io where "blk_status_t status" is written by an asynchronous completion routine and "atomic_t io_count" is modified synchronously - another example is the structure dm_buffer where "unsigned hold_count" is modified synchronously from process context and "blk_status_t write_error" is modified asynchronously from bio completion routine
This patch fixes the bug by changing the type blk_status_t to 32 bits if we are on Alpha and if we are compiling for a processor that doesn't have the byte-word-extension.
Signed-off-by: Mikulas Patocka mpatocka@redhat.com Cc: stable@vger.kernel.org # 4.13+ Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/linux/blk_types.h | 5 +++++ 1 file changed, 5 insertions(+)
--- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -20,8 +20,13 @@ typedef void (bio_end_io_t) (struct bio
/* * Block error status values. See block/blk-core:blk_errors for the details. + * Alpha cannot write a byte atomically, so we need to use 32-bit value. */ +#if defined(CONFIG_ALPHA) && !defined(__alpha_bwx__) +typedef u32 __bitwise blk_status_t; +#else typedef u8 __bitwise blk_status_t; +#endif #define BLK_STS_OK 0 #define BLK_STS_NOTSUPP ((__force blk_status_t)1) #define BLK_STS_TIMEOUT ((__force blk_status_t)2)